c#一个popup问题 ：Button_Click_send中如何取得textbox1的内容啊

为了能够获得，我把 TextBox textbox1 = new TextBox()做成全局变量的话，依次点击 error_Click，Button_Click_send是能够获得的，但是再次点击error_Click就会出错，怎么办啊
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TextBox textbox1 = new TextBox();
private void error_Click(object sender, EventArgs e)
{
Popup p = new Popup();

Border border = new Border();
border.BorderBrush = new SolidColorBrush(Colors.LightGray);
StackPanel panel1 = new StackPanel();
panel1.Background = new SolidColorBrush(Colors.LightGray);
BuButton button2 = new Button();
button2.Content = "Send";
button2.Click += new RoutedEventHandler(Button_Click_send);
textbox1.Margin = new Thickness(5.0);
textbox1.Height = 350;
textbox1.Width = 370;
panel1.Children.Add(textbox1);
panel1.Children.Add(button2);
border.Child = panel1;
p.Child = border;
p.VerticalOffset = 50;
p.HorizontalOffset = 50;
p.IsOpen = true;
}
private void Button_Click_send(object sender, RoutedEventArgs e)
{
EmailComposeTask email = new EmailComposeTask();
email.To = "";
email.Subject = "";
email.Body = textbox1.Text ;
email.Show();
}

button2.Click += new RoutedEventHandler(Button_Click_send);第一次 button2 已经注册过 Button_Click_send 这个事件了，第二次还要注册当然会出错。

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